After the death of her foster father, Fanny is employed by her real father (a Cabinet minister) as a servant, and uncovers various things about his wife and her lover Lord Manderstoke that might best have stayed under wraps.

Fanny by Gaslight was made to cash in on the success of The Man in Grey (d. Leslie Arliss, 1943), and used many of the same ingredients: lead actors Phyllis Calvert, James Mason and Stewart Granger, a nineteenth-century setting that provided plenty of opportunities for lavish costume display, a similar mix of archetypal "good" and "bad" male and female characters, and a surprisingly racy and distinctly un-British attitude towards sexuality.

Anthony Asquith was the biggest "name" director to work on a Gainsborough melodrama, and his experience helped wring rather more impressive production values than the budget might otherwise have allowed. There are also some strikingly imaginative touches, such as the face of Clive Seymore (Stuart Lindsell) literally fragmenting in the mirror prior to his suicide, paralleling his mental breakdown as he realises he's run out of options.

Where Fanny by Gaslight is a clear advance on The Man in Grey is that it has a much more sophisticated understanding of the social context underlining both the drama itself and the demands of the 1944 audience.

Harry's speech about how class divisions would be abolished within a hundred years, allowing him to marry whoever he pleases, was clearly aimed at a largely female audience that had itself set aside social differences as a result of the war - and the film underscores this by placing all the working-class characters in an overwhelmingly positive light, from the floozies in the Hopwood Shades to the lovable old retainer Chunks (Wilfrid Lawson), while making it clear that their lot in life is to be used and abused by their social superiors.

The film's attitude towards sexuality is rather more complex and intriguing. From the opening scenes of Fanny's discovery of the Shades (the word is never used, but it's clearly a brothel) and the fact that her mother was less than faithful, through to James Mason's portrait of Lord Manderstoke as a man blending absolute moral corruption with devastating sensuality, Fanny by Gaslight both shies away from and celebrates the liberating power of living dangerously in an environment where the slightest transgression could bring about social catastrophe.

The film is further enriched by a decidedly ambiguous ending, which would also have had contemporary echoes, as much of the audience would have had a similar experience to Fanny in terms of losing or nearly losing a loved one.